What Can a Kidney Ultrasound Show—and What Can’t It Tell You?

Anthony Ofori | Medical Graduate in General Medicine | Founder, WellNest Central
Last updated: October 12, 2026

This article provides general health education for adults and does not replace individual medical advice.

Your clinician has requested a kidney ultrasound. You may be wondering whether it will explain a raised creatinine result, detect a stone, or tell you exactly how well your kidneys work.

A kidney ultrasound can provide useful information about structure, including kidney size, position, and certain visible abnormalities. However, it cannot answer every question about kidney health. A normal scan does not replace blood and urine testing.

Knowing what the examination is designed to show makes both the appointment and the report easier to understand.

What is a kidney ultrasound?

Ultrasound uses sound waves to create images. A trained professional moves a handheld probe over your skin after applying gel. The examination does not use ionizing radiation.

The NIDDK’s urinary tract imaging guide describes ultrasound as a way to examine the structure of the kidneys and other parts of the urinary system.

Your appointment may include the bladder as well as the kidneys. The precise protocol depends on why the test was requested. “Kidney scan” is also used loosely for other examinations, so check that your appointment actually says ultrasound.

What can a kidney ultrasound show?

Kidney size and position

The scan can show where the kidneys are and measure their size. These findings can help your clinician assess structural differences or changes that may relate to your medical history.

A measurement is interpreted in context. One dimension on a report cannot independently establish your kidney function or tell you whether treatment is necessary.

Widening of the urine-collecting system

Ultrasound can identify dilation inside the kidney, often described as hydronephrosis. This may raise concern about impaired urine drainage, but the finding needs interpretation alongside symptoms and other tests.

The next question is why it is present and whether it represents a significant obstruction. The scan does not always identify the exact cause, and additional assessment may be needed.

Some stones and other visible abnormalities

Kidney stones may be visible, and the scan can sometimes show indirect evidence of a blockage. However, ultrasound does not detect every stone or establish the cause of every episode of flank pain.

Depending on the clinical question, another type of imaging may provide more useful detail. A request for a CT scan after ultrasound does not automatically mean the first examination was performed badly; the tests have different strengths.

Cysts and masses

Ultrasound can identify fluid-filled cysts and some other lesions. A finding may need further imaging to determine its nature, particularly when it does not have the typical appearance of a simple cyst.

A report mentioning a lesion is not, by itself, a cancer diagnosis. Ask what the radiologist concluded and what follow-up, if any, was recommended.

Does a kidney cyst always mean kidney disease?

No. The NIDDK explains that simple kidney cysts are usually harmless and are different from inherited polycystic kidney disease.

Some are found incidentally during imaging for another reason. Others need review because of symptoms or a less typical appearance. The word “simple” matters, and you should not assume every cyst belongs to the same category.

Ask whether the finding needs monitoring, whether it plausibly explains your symptoms, and whether previous imaging is available for comparison. This is more useful than searching every unfamiliar report term in isolation.

What can’t a normal ultrasound tell you?

A normal-looking kidney can still have a problem with filtration or leakage of protein. Ultrasound cannot directly replace an eGFR result or measure how much albumin is passing into your urine.

The NIDDK’s kidney-testing guidance identifies blood testing for filtration and urine testing for albumin as key parts of evaluating kidney health.

For example, someone may have albumin in the urine without a structural abnormality visible on ultrasound. Another person may have a simple cyst with otherwise reassuring kidney tests. Neither situation is contradictory.

Our guide to three complementary kidney tests explains why several types of information are often needed.

How to prepare for the appointment

Read the instructions from the imaging department. Some examinations require a full bladder, and some may include fasting instructions, particularly if other abdominal organs are being examined.

Do not follow a generic instruction to drink a large volume if you have a prescribed fluid restriction. Contact the department and explain your situation so it can give suitable directions.

Wear clothing that allows access to your abdomen and back. Bring your appointment details and mention mobility difficulties or pain that could make lying in a particular position uncomfortable.

If blood or urine tests are also scheduled, check their preparation separately. Our urine albumin test preparation guide covers sample collection questions.

What happens during the scan?

You will usually lie on an examination couch while gel is applied and the probe is moved over the relevant areas. You may be asked to turn, change position, or briefly hold your breath to improve the view.

The scan itself is generally straightforward, though pressure from the probe may feel uncomfortable over a tender area. Tell the professional performing it if something hurts rather than trying to stay silent.

If the bladder is included, you may be asked to empty it and return for another measurement. Ask when the written report will reach the clinician who ordered the test.

How to discuss the report

Start with the report’s conclusion or impression, then ask how it relates to the reason for testing. Useful questions include: “Was the suspected problem found?” “Were both kidneys adequately seen?” and “Do I need further imaging or laboratory tests?”

If the report is reassuring but symptoms continue, return to your clinician. A normal scan does not mean ongoing pain, blood in urine, or changing kidney results should be ignored.

When not to wait for a routine scan

Seek urgent medical advice for severe flank pain with fever, inability to pass urine, or significant illness with vomiting. Visible blood in urine also warrants medical assessment, even if it later clears.

An ultrasound is one part of an investigation. Its greatest value comes from combining the images with your symptoms, examination, and laboratory results to answer a specific clinical question.

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